JP2020047907A - Coupling inductor and switching circuit - Google Patents

Abstract

To provide a multi-phase coupling inductor capable of achieving stable performance and size and cost reductions.SOLUTION: A coupling inductor 10 is used for a multi-phase switching circuit of interleave method. The coupling inductor 10 is configured to constitute an inductor unit 1 formed from a core 7 and a winding 8 wound around two positions of the core 7. Three inductor units 1 are arranged on an inductor installation surface and the two windings 8 wound around the common core 7 of the respective inductor units 1-3 are connected to each of different phases of the switching circuit.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a coupling inductor and a switching circuit having the coupling inductor.

  2. Description of the Related Art In recent years, power conversion circuits of transportation equipment (for example, hybrid cars, electric vehicles, fuel cell vehicles, etc.) and electronic equipment (for example, smartphones, personal computers, etc.) incorporating a storage battery have been reduced in size and weight while maintaining high output, that is, high power conversion circuits. Power density is required.

  An interleave scheme has been attracting attention as a circuit scheme for realizing high power density. The interleave method is a control method in which a power supply is divided into a plurality of systems, each phase has a phase difference, and ripples and the like are canceled each other. For example, in a two-phase interleaving method, a ripple is offset by giving a 180 ° phase difference to the current phase. By employing the interleaving method, it is possible to reduce the size and weight of the output smoothing capacitor and to reduce the ripple.

  On the other hand, in the interleave method, since the number of components of the inductor increases, there is a limit to the increase in power density. Therefore, in addition to the interleaving method, the use of a coupling inductor that magnetically couples and uses inductors of each phase is being studied. The following effects are expected by using a coupled inductor.

(1) In the conventional interleaving method, the number of inductors equal to the number of paralleled phases increases, but by using a coupled inductor, the windings of each phase can be integrated into a single magnetic core. Therefore, the number of parts can be reduced.

(2) In general, the core size is largely related to the maximum magnetic flux in the core. In a coupled inductor that is magnetically coupled by reverse coupling, DC magnetic fluxes generated from DC currents of windings are mutually canceled while parallel inductors are used. Since the alternating magnetic flux generated between the integrated circuits can be shared, the magnetic flux in the core can be reduced, and the size of the inductor can be reduced.

  As an example of the coupling inductor described above, as described in Patent Document 1 below, two E-shaped cores, an I-shaped core sandwiched between two E-shaped cores, and wound with two coils, 2 having a first gap provided between the center leg of one E-shaped core and the I-shaped core, and a second gap provided between the center leg of the other E-shaped core and the I-shaped core. Phase coupled inductors are known.

  In recent years, it has been studied to apply the two-phase interleaved coupled inductor described in Patent Literature 1 to a three-phase interleaved circuit for use. By expanding to three phases, the input current can be shunted compared to the case of two phases, so that a further increase in capacity can be realized. Further, the capacity of the output-side smoothing capacitor can be further reduced.

  As disclosed in Patent Document 2 below, as a three-phase coupled inductor, there is known an inductor using a three-axis core in which three shafts are arranged along three axes orthogonal to each other and integrated. ing.

Japanese Patent No. 5934001 JP 2011-204946 A

  However, verification of a coupled inductor suitable for a three-phase interleaved circuit has not been sufficiently advanced. For example, even if another leg is added to the core of the two-phase coupled inductor described in Patent Literature 1, the magnetic path length and the mutual inductance of each phase cannot be made the same, and the magnetic flux bias and the Loss occurs and symmetry cannot be maintained. Therefore, the performance as a coupling reactor decreases.

  When the triaxial core of Patent Document 2 is used, since the triaxial core is provided with protrusions that protrude in six directions from a common central portion, the core shape is complicated, and the core production is extremely difficult. Requires many man-hours. Therefore, the manufacturing cost of the coupled inductor increases.

  Patent Document 2 discloses a three-phase coupled inductor, but does not disclose a coupled inductor having four or more phases.

  Therefore, an object of the present invention is to provide a small and inexpensive multi-phase coupled inductor having stable performance.

  In order to solve the above problems, the present invention relates to a coupled inductor used in an interleaved multi-phase switching circuit, wherein an inductor unit is formed by a core and a plurality of windings wound around a plurality of locations of the core. A plurality of the inductor units (for example, three when used in a three-phase switching circuit), and the plurality of windings wound around a common core of each inductor unit are respectively connected to different phases of the switching circuit. It is characterized by being performed.

  By winding a plurality of windings around a plurality of portions of the core in this manner, each inductor unit magnetically couples the plurality of inductors, and is equivalently configured with one inductor. In addition, a plurality of windings wound around a common core of each inductor unit are connected to different phases of the switching circuit. In such a configuration, by driving the multi-phase switching circuit by shifting the phase, the inductor currents of the respective phases interfere with each other, and the alternately excited magnetic flux links with other windings. As a result, the inductor current waveform is driven at a multiple of the switching frequency equal to the number of phases (three times in the case of a three-phase switching circuit). During driving, the DC magnetic flux cancels each other in each inductor unit, while the AC magnetic flux circulates in the magnetic flux path formed in each core while strengthening or canceling each other in the core of each inductor unit. . Therefore, the magnetic flux generated in each core can be reduced by increasing the inductance of each inductor unit, and the core can be downsized.

  Further, with the above configuration, it is easy to make the magnetic path length and the mutual inductance of each inductor unit the same length and value. Therefore, the performance as the coupling inductor can be stabilized.

  In particular, with the above configuration, the inductor units are in a state of being electrically connected, but are not in a state of being mechanically connected, and are in a state of being separable from each other. Therefore, the arrangement position of each inductor unit can be freely selected. Therefore, the degree of freedom in the arrangement of the multi-phase coupled inductor can be increased, and restrictions on the installation space can be reduced.

  In such a configuration, it is preferable that the plurality of windings wound around a common core be connected such that DC components of magnetic flux generated by the plurality of windings cancel each other out at the core. Further, it is preferable to connect windings of different inductor units in parallel to the same phase of the switching circuit.

  Further, it is preferable that the core of each inductor unit is formed in an endless loop shape having no air gap. Accordingly, the leakage magnetic flux can be reduced, so that the heat generation in the winding due to the leakage magnetic flux reaching the winding and generating an eddy current in each winding can be suppressed.

  In the coupling inductor, since it is necessary to use the leakage inductance, it is necessary not to make the coupling coefficient too high. Of course, if the coupling coefficient is too low, the effect of magnetic coupling cannot be obtained. Therefore, the coupling coefficient of each inductor unit is preferably 0.3 or more and 0.85 or less.

  The core is preferably formed of a soft magnetic powder with an insulating coating. This makes it easier to generate magnetic flux leakage than when ferrite is used as the core material. Therefore, even if an air gap is not provided, an appropriate leakage flux can be generated in the entire core, and an appropriate coupling coefficient can be easily obtained. Further, it is not necessary to separately provide a path through which the leakage magnetic flux flows. Therefore, it is possible to reduce the size of the multi-phase coupled inductor while preventing heat generation of the winding due to leakage magnetic flux around the air gap. The initial magnetic permeability of the core using the soft magnetic powder with the insulating coating is preferably 30 or more and 200 or less.

  By forming an interleaved multi-phase switching circuit using the above-described coupled inductors, high power density of the circuit can be achieved.

  According to the present invention, it is possible to provide a small and inexpensive multiphase coupled inductor having stable performance.

It is a perspective view showing the three-phase coupling inductor concerning this embodiment. It is a perspective view which shows one inductor unit which comprises a coupling inductor. FIG. 3 is a circuit diagram illustrating an interleaved three-phase boost chopper circuit using a three-phase coupled inductor. FIG. 4 is a plan view showing an arrangement of each inductor unit in a three-phase coupled inductor. It is a table | surface which shows the test result of a confirmation test. It is a figure showing the current waveform of a three-phase coupling inductor. FIG. 2 is a circuit diagram showing an interleaved four-phase boost chopper circuit using a four-phase coupled inductor. It is a perspective view showing a four-phase coupling inductor. FIG. 5 is a diagram illustrating a current waveform of a four-phase coupled inductor. 9 is a table summarizing the relationship between the number of phases and various characteristics when the coupling inductor is multi-phased. It is a top view showing other embodiments of a four-phase coupling inductor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a multi-phase coupled inductor, particularly a three-phase coupled inductor 10 according to the present embodiment.
As shown in FIG. 1, the three-phase coupled inductor 10 includes three inductor units (a first inductor unit 1, a second inductor unit 2, and a third inductor unit 3). Each of the inductor units 1 to 3 has a common configuration, and each has a core 7 and a plurality of windings 8 wound around the core 7 at two locations.

In the following description, the number of the inductor unit to which each core belongs is appended by a suffix after the code 7 representing the core. That is, reference numeral ₇₁ denotes the core of the first inductor unit 1, reference numeral 7 ₂ represents the core of the second inductor unit 2, reference numeral 7 ₃ represents the core of the third inductor unit.

FIG. 2 shows a perspective view of the first inductor unit 1 which is one of the three inductor units 1 to 3.
As shown in FIG. 2, the core 7 ₁ of the first inductor unit 1 includes a pair of legs 71 and a pair of connecting portions 72 which are bridged between one end and between the other end of the leg portion 71 in a pair . In the present embodiment illustrates well as parallel to the pair of legs 71, a core ₇₁ forming a whole in a rectangular frame shape connecting portion 72 arranged in a direction perpendicular from the leg portion 71. The core _71, it is possible to employ any form as long as it has a closed loop-like form, other than the rectangular frame shape, may be employed for example an annular core (toroidal core). The core 7 _1, the air gap is not provided.

As shown in FIG. 1, with the remainder of the inductor unit (second inductor unit 2 and the third inductor unit 3), the first core ₇₁ of the inductor unit 1 and the same shape core 7 _2, 7 _3, respectively. Air gap the cores 7 _2, 7 ₃ are not provided. In FIG 1, a first inductor unit leg 71 of the core 7 ₁ only 1 indicated by a broken line, the core 7 _2, 7 ₃ other inductor units 2 and 3, for simplification of the drawing, the leg The illustration of the unit 71 is omitted.

Core 7 _{1-7 3,} both after compression molding soft magnetic powder using a mold, is manufactured by applying an annealing process to the powder compact. As the soft magnetic powder, use a soft magnetic powder with an insulating coating obtained by coating an insulating coating on a soft magnetic metal powder composed of pure iron, amorphous, soft magnetic alloy (such as Sendust, Permalloy), or nanocrystalline. Can be. As the insulating coating, a metal oxide or semi-metal oxide such as Al ₂ O ₃ , Y ₂ O ₃ , MgO, ZrO ₂ , a glass material, or a mixture of these and a resin material as a binder is used. used. With annealing, the binder component is decomposed and volatilizes as a gas. The initial magnetic permeability (meaning the relative magnetic permeability at a magnetic field of 0 A / m) of the core using the soft magnetic powder with the insulating coating is preferably 30 or more and 200 or less. Further, the leg portion 71 and the connecting portion 72 can be formed of different materials in addition to the same material.

The legs 71 of the core 7 _{1-7 3,} one by one winding 8 are respectively mounted. Thus, common core 7 _{1-7 3} wound on the winding 8 is in a state of being magnetically coupled. Each winding 8 has the same number of turns, is formed of the same conductive material, and has the same cross-sectional dimension. Therefore, each winding 8 has equal inductance. The two windings 8 wound around the same core are connected so as to have opposite polarities. More specifically, when the flow of direct current to each of the two windings 8 wound on the same core are connected in parallel, the magnetic flux directions cancel each other in the core 7 ₁ ~7 ₃ φ ( The windings 8 are connected so that (see FIG. 1) occurs.

  The two windings 8 wound around the common core 7 in each of the inductor units 1 to 3 will be described in detail later, but two different phases of a three-phase (u-phase, v-phase, and w-phase) switching circuit will be described. Connected to. That is, one of the two windings 8 of the first inductor unit 1 is connected to the u-phase and the other is connected to the w-phase, and one of the two windings 8 of the second inductor unit 2 is connected to the u-phase. Phase and the other is connected to the v-phase. One of the two windings 8 of the third inductor unit 3 is connected to the v-phase, and the other is connected to the w-phase. In FIG. 1, the connection mode described above is represented by parenthesizing the connection destination phase after the reference numeral 8 representing each winding.

The coupled inductor 10 described above is, for example, in each of the inductor units 1 to 3, in a state where one end of the two legs 71 is fixed to one connecting portion 72, the winding 8 wound in advance is connected to each leg. It is manufactured by inserting it around the outer periphery of the base 71 and then fixing the other connecting part 72 to the other end of each leg 71. The fixing of the leg portion 71 and the connecting portion 72 can be performed by, for example, bonding. Of course after forming each core 7 _{1-7 3} together, may be wound legs 71 wound around 8.

In the coupling inductor 10 manufactured in this way, since it is necessary to use the leakage inductance, it is necessary not to make the coupling coefficient too high. Of course, if the coupling coefficient is too low, the effect of magnetic coupling cannot be obtained. From the above viewpoint, the coupling coefficient of each of the inductor units 1 to 3 is preferably set in a range of 0.3 to 0.85 (preferably 0.3 to 0.75). As described above, by using the soft magnetic powder with the insulating coating as the material of the core 7, the adjustment of the coupling coefficient becomes easy, and the coupling coefficient within this range can be easily obtained. The coupling coefficients of the inductor units 1 to 3 have the same value. Note that the coupling coefficient here is obtained from the following equation in accordance with the open / short method specified in JIS C 5321.
Coupling coefficient k = (1-Lsc / Lop) ^1/2
Here, Lsc is a short-circuit L value (two lines are short-circuited), and Lop is an open L value.

  The coupling inductor 10 described above is arranged in a three-phase (u-phase, v-phase, and w-phase) switching circuit that employs an interleaving method illustrated in FIG. The switching circuit here means a circuit through which a high-frequency current flows with switching. FIG. 3 shows a schematic configuration of a power supply circuit, particularly a DC-DC boost chopper circuit, as an example of the switching circuit.

  As shown in FIG. 3, one end of each winding 8 of the coupled inductor 10 is connected to the power source E in parallel. At this time, as described above, the windings 8 of the respective homologous numbers (two) provided in the different inductor units 1 to 3 are connected to each phase (u, v, w) of the switching circuit. . Specifically, of the two windings 8 of the first inductor unit 1, one 8 (u1) is connected to the u phase, and the other 8 (w2) is connected to the w phase. One (8) (u2) of the two windings 8 of the second inductor unit 2 is connected to the u-phase, and the other 8 (v1) is connected to the v-phase. Further, one (8) (v2) of the two windings 8 of the third inductor unit 3 is connected to the v-phase, and the other 8 (w1) is connected to the w-phase. Thus, each winding 8 of the coupled inductor 1 is cyclically connected to each phase of the circuit. Further, two windings (for example, the winding 8 (u1) and the winding 8 (u2)) connected to the same phase of the switching circuit are connected in parallel in each phase.

  The other ends of the two windings 8 (u1) and 8 (u2) connected to the u-phase are connected to the anode of the first diode D1 and one end of the first switching element Q1, respectively, and are connected to the two v-phases. The other ends of the windings 8 (v1) and 8 (v2) are connected to the anode of the second diode D2 and one end of the second switching element Q2. The other ends of the two windings 8 (w1) and 8 (w2) connected to the w-phase are connected to the anode of the third diode D3 and one end of the third switching element Q3. The other ends of the switching elements Q1 to Q3 are connected to the ground side. Each of the switching elements Q1 to Q3 repeats the opening / closing operation at a constant cycle according to a control signal from a control device (not shown). At this time, the switching elements Q1 to Q3 repeat the opening / closing operation by shifting the phase by 120 °.

  The voltage and current output from the cathodes of the diodes D1 to D3 are smoothed by the smoothing capacitor C and consumed by the load R.

  In the case of the single-phase system in which the boost chopper circuit is configured as a single unit (one phase), the current sent to the smoothing capacitor on the output side is intermittent, and the smoothing capacitor repeats intense charging and discharging. Therefore, a large capacity is required for the smoothing capacitor, and the size of the smoothing capacitor increases. On the other hand, in the interleave system (multi-phase system) of FIG. 3 in which circuits are operated in parallel, control is performed so that each phase is alternately switched. The size of the capacitor C can be reduced.

  In addition, since the interleave circuit is expanded to three phases, the input current can be shunted as compared with the two-phase interleave circuit, so that the capacity can be further increased. Further, the capacity of the output-side smoothing capacitor can be further reduced.

In the three-phase coupled inductor 1 according to the present embodiment, each of the inductor units 1 to 3 magnetically couples two inductors and is equivalently constituted by one inductor. Further, two windings (for example, 8 (u1) and 8 (w2)) wound around a common core of each of the inductor units 1 to 3 are connected to two different phases (for example, u-phase and w-phase) of the switching circuit. Connected to each other. That is, two windings connected to different phases are magnetically coupled. In such a configuration, by driving the three-phase interleaved boost chopper circuit by shifting the current phase, the inductor currents I _u , I _v , and I _w of each phase interfere with each other, and the alternately excited magnetic flux causes another. It is a form that links with the winding of. This results in a state where the inductor current waveform is driven at three times the switching frequency.

As shown in FIG. 1, during the operation of the coupled inductor 10, the DC magnetic flux φ generated from the inductor average current in each of the inductor units 1 to 3 cancels each other. On the other hand, the AC magnetic flux is circulated to constructive or an endless loop magnetic flux path formed in the core 7 _{1-7 3} while cancel shared within the core of each inductor unit 1-3. As described above, by canceling out the DC magnetic flux, the magnetic flux in the core can be reduced, but the magnetic flux path in which the magnetic flux of the AC component circulates is formed, so that the inductance of each of the inductor units 1 to 3 increases. Thus, the core 7 _{1-7 3} can be miniaturized by reducing the magnetic flux generated in the core 7 _{1-7 3,} ripple width is small, to provide a coupled inductor 10 small that improved the superimposition characteristics It becomes possible.

  Further, in the coupled inductor 10 of the present embodiment, since the inductor units 1 to 3 are formed in the same structure, the magnetic path lengths and the mutual inductances of the inductor units 1 to 3 can be set to the same value. Therefore, the performance as the coupled inductor 10 can be stabilized.

Further, the air gap is not formed in the magnetic flux path of the core 7 _{1-7 3,} each core 7 _{1-7 3} to form a closed magnetic path, leakage flux is reduced. Therefore, it is possible to prevent the leakage magnetic flux from reaching each winding 8 and generating heat in the winding 8 due to the generation of eddy current in each winding. Also, a decrease in inductance can be prevented. This makes it possible to provide a three-phase coupled inductor 10 that is small in size and generates little heat in the winding 8.

When forming a general ferrite as the material of the core 7 _{1-7 3,} initial permeability of the ferrite is high (about 2300) for, leakage flux is reduced. Therefore, the ripple width cannot be suppressed unless the inductor is increased in size, and the demand for downsizing cannot be met. It is effective to provide an air gap in the magnetic flux path in order to increase the leakage magnetic flux, but this causes a problem of heat generation in the winding 8 as described above. In contrast, as in this embodiment, by forming the core 7 _{1-7 3} initial permeability 30 to 200 by using the insulating film-containing soft magnetic powder, binding moderate even if not provided an air gap A coefficient (0.30 to 0.85) can be obtained. Therefore, it is possible to provide a small-sized coupling inductor 10 having a stable ripple suppression effect and a DC current superimposition characteristic while preventing heat generation in the winding 8 which becomes a problem when an air gap is provided.

  In the coupled inductor 1 of the present embodiment, each of the inductor units 1 to 3 is in an electrically connected state through the wiring, but is not in a state of being mechanically connected. That is, the individual inductor units 1 to 3 are in a separable state. Therefore, each of the inductor units 1 to 3 can be arranged at an arbitrary position. For example, as shown in FIG. 1, it is possible to adopt a form in which each of the inductor units 1 to 3 is arranged at each vertex position of a triangle in a plan view viewed from the winding axis direction, or as shown in FIG. It is also possible to adopt a form in which the inductor units 1 to 3 are developed in a line and arranged in a plane such that the winding axes are located on the same plane. Further, it is possible to arrange one inductor unit at a position apart from the other two inductor units. Therefore, the degree of freedom in the arrangement of the three-phase coupled inductor 10 can be increased, and the restriction on the installation space can be reduced.

  In particular, in the arrangement shown in FIG. 4, the coupling inductor 10 is positioned on the same plane where each winding axis is parallel to the inductor installation surface (100: see FIG. 7) provided on a circuit board or the like. It becomes possible to arrange so that. In this case, since the distance from each winding 8 to the inductor installation surface is made uniform, the heat radiation of each winding 8 can be made uniform. Therefore, the temperature rise width of each winding 8 can be made uniform, and variations in the magnetic characteristics of each winding 8 can be suppressed. In addition, since there is no need to install a separate component for heat dissipation, the overall size of the coupled inductor 10 can be reduced.

As the core 7 _{1-7 3,} can be adopted existing core having a simple form of U-U-shaped core and such toroidal core form endless loops. Therefore, it is possible to cost reduction complex and it is not necessary to prepare a core of three-dimensional structure, the manufacturing cost of the core 7 _{1-7 3} as described in Patent Document 2.

  Next, a confirmation test for confirming the effect of the coupled inductor 10 according to the present embodiment was performed, and the details and results will be described.

  In this confirmation test, the coupled inductor 10 shown in FIG. 1 is used in the three-phase interleaved boost chopper circuit shown in FIG. 3, and the output voltage when the duty ratio is changed is measured. The inductance of each winding 8 is 200 μH, the coupling coefficient of each of the inductor units 1 to 3 is 0.7, and the input voltage is 400 V DC. The phase shift between the phases is 120 °, and switching is performed at 50 kHz.

  As is clear from the test results shown in FIG. 5, according to the present embodiment, the output voltage increases as the duty ratio increases. Therefore, it was confirmed that even when the coupled inductor 1 of the present embodiment was used, the operation as a booster circuit was performed without any problem.

FIG. 6 shows a current I _u of the u-phase, a current I _u1 of the winding 8 (u1) connected to the u-phase, and a current of the winding 8 (u2) connected to the u-phase in the switching circuit shown in FIG. It shows the result of measuring I _u2 (coupling coefficient is 0.5, frequency is 55 kHz, and duty ratio is 0.65).

As is clear from FIG. 6, the average current of each winding and the ripple width of each winding current are each half of I _u . In each winding current, regions X and Y having gentle slopes are generated, and the effect of magnetic coupling of the windings 8 (u1) and 8 (u2) can be seen.

  In the above description, the three-phase coupled inductor 10 is illustrated, but by adopting a similar configuration, a coupled inductor having four or more phases can be provided.

  In this multi-phase coupled inductor, “the number of phases × (the number of phases−1) / 2” cores and inductor units are used. For example, three cores and inductor units are used for three phases, six for four phases, ten for five phases, fifteen for six phases, and twenty-one for seven phases. Further, since two windings 8 are mounted on each core, the number of windings of the entire coupled inductor is twice the number of cores.

FIG. 7 shows a four-phase coupled inductor 11 as an example of a multi-phase coupled inductor. The coupled inductor 11 includes first to sixth inductor units 1 to 6. Each inductor unit 1-6 has the same structure as the inductor unit 1-3 described previously in 3-phase coupled inductor 10 described, respectively core 7 and _{(7 1 ~7 6), 180} ° opposed position of the core 7 And two windings 8 arranged in the same direction. FIG. 7 illustrates a case where a toroidal core is used as each core 7.

  FIG. 8 shows an interleaved four-phase switching circuit using the four-phase coupled inductor 11 described above. As shown in FIG. 8, three windings 8 are connected in parallel to each of the four phases (a phase, b phase, c phase, and d phase). That is, the windings 8 (a1), 8 (a2), 8 (a3) are connected to the a-phase, and the windings 8 (b1), 8 (b2), 8 (b3) are connected to the b-phase. . The windings 8 (c1), 8 (c2), 8 (c3) are connected to the c-phase, and the windings 8 (d1), 8 (d2), 8 (d3) are connected to the d-phase.

  The switching elements Q1 to Q4 of the multi-phase switching circuit perform opening and closing operations such that the current phases are shifted by an angle obtained by dividing 360 ° by the number of phases. Therefore, in the four-phase switching circuit, each of the switching elements Q1 to Q4 repeats the opening and closing operation by shifting the phase by 90 °.

Similarly to the three-phase coupled inductor, in the four-phase coupled inductor, the two windings 8 (for example, 8 (a1) and 8 (b1)) wound around the common core 7 are among the four-phase switching circuits. It is connected to two different phases (a phase, b phase). Conversely, of the twelve windings 8 shown in FIG. 8, two windings connected to different phases are magnetically coupled by being wound around a common core 7. For example, two windings of the combinations listed below are magnetically coupled by being mounted on a common core 7 (see FIG. 7).
-Winding 8 (a1) and winding 8 (b1)
-Winding 8 (a2) and winding 8 (c1)
-Winding 8 (a3) and winding 8 (d1)
-Winding 8 (b2) and winding 8 (c2)
-Winding 8 (b3) and winding 8 (d2)
-Winding 8 (c3) and winding 8 (d3)

FIG. 9 shows the current I _a of the a-phase, the current I _{a1 of} the winding 8 (a1) connected to the a-phase, and the current of the winding 8 (a2) connected to the a-phase in the switching circuit shown in FIG. It shows the result of measuring I _a2 and the current I _{a3 of} the winding 8 (a3) connected to the a-phase (coupling coefficient is 0.5, frequency is 55 kHz, and duty ratio is 0.65). .

As is clear from FIG. 9, the average current of each winding and the ripple width of each winding current are 1/3 of _Ia . In addition, as in the case of three-phase winding, a region having a gentle slope is generated in each winding current, and the effect of magnetically coupling the windings 8 (a1), 8 (a2), and 8 (a3) is seen. be able to.

  The same operational effects as those of the previously described three-phase coupled inductor 10 can also be obtained in the coupled inductor 11 having the four phases. Even when the number of phases is increased to five or more, the same operation and effect can be obtained by connecting the two windings 8 wound around the common core 7 to two different phases.

  FIG. 10 is a table summarizing changes in various characteristics of the multi-phase coupled inductor when the number of phases is changed.

  In each item of FIG. 10, “parallel number” is the number of windings to be connected in parallel to each phase. “I (phase)” represents the current value of each phase, and “I (winding)” represents the current value of each winding. “R” represents the sum of the resistance values of the windings, and “P (copper)” represents the heat dissipation (copper loss) of the windings per core. L represents an inductance value required for each phase number, and “copper wire diameter” represents a diameter dimension of a copper wire forming a winding required from the value of “P (copper)”. “H” is represented by H = N × I / l (1 is a magnetic path length, N is the number of turns, I is a current value), and the smaller this value is, the better the DC superimposition characteristic is. “ΔI” represents the ripple width in each core, and ΔB represents the amount of change in magnetic flux density (ΔB = μ × H). “P (iron)” represents the heat radiation amount (iron loss) of the core of the entire coupled inductor. In FIG. 10, the value of each item in the one-phase switching circuit is 1.

  From the value of “copper S” in FIG. 10, it can be understood that, in the multiphase coupled inductor, the copper wire diameter can be reduced as the number of phases increases. Therefore, as the number of phases increases, the manufacture of the winding becomes easier, and the cost can be reduced. It can also be understood from the value of “H” that the superimposed magnetizing force decreases as the number of phases increases, and the DC superimposition characteristics improve. Further, it can be understood from the value of “L” that the required L value increases as the number of phases increases, and that the iron loss can be reduced as the number of phases increases from the values of “ΔB” and “P iron”. Further, from the result of “P (copper)”, as the number of phases increases, the copper loss (heat dissipation of the winding) in each core 7 decreases. Therefore, heat management can be facilitated by dispersing the heat radiation of the entire coupled inductor.

  In FIG. 7, the inductor units (1 to 6) are arranged in a plane such that the winding axes are located on the same plane. Therefore, when the inductor units (1 to 6) are arranged on the inductor installation surface 100, the distance from each winding 8 to the inductor installation surface 100 is made uniform. Therefore, the heat radiation of each winding 8 can be made uniform, the temperature rise of each winding 8 can be made uniform, and the variation in the magnetic characteristics of each winding 8 can be suppressed. Further, since the coupling inductor 11 has a planar shape, the height dimension can be reduced.

  As shown in FIG. 11, the inductor units (1 to 6) may be arranged in a line on the inductor mounting surface 100. As described above, the multi-phase coupled inductor of the present embodiment has an advantage that the degree of freedom in shape is high because each inductor unit (1 to 6) is in a separable state.

  In the above description, the case where the coupling inductors 10 and 11 are arranged in the step-up chopper circuit has been exemplified. However, the coupling inductors 10 and 11 described above are arbitrary as long as they have an interleaved multi-phase switching circuit. Can be used for circuits. For example, the present invention can be used for a transformer application (regardless of step-down or step-up) in a PFC (power factor correction) circuit, a converter circuit, an inverter circuit, and the like, an inverter application, a converter application, and the like.

REFERENCE SIGNS LIST 1 first inductor unit 2 second inductor unit 3 third inductor unit 4 fourth inductor unit 5 fifth inductor unit 6 sixth inductor unit 7 core 8 winding 10 coupled inductor (three-phase)
11 Coupled inductor (4 phase)
71 Leg 72 Connecting part

Claims (9)

In a coupled inductor used for an interleaved multi-phase switching circuit,
An inductor unit is formed by the core and a plurality of windings wound around a plurality of locations of the core,
Comprising a plurality of the inductor units,
The coupled inductor, wherein the plurality of windings wound around a common core of each inductor unit are connected to different phases of the switching circuit, respectively.   The coupled inductor according to claim 1, wherein the plurality of windings wound around a common core are connected such that DC components of magnetic flux generated in the plurality of windings cancel each other out at the core.   3. The coupled inductor according to claim 1, wherein windings of different inductor units are connected in parallel to the same phase of the switching circuit.   The coupled inductor according to any one of claims 1 to 3, wherein a core of each inductor unit is formed in an endless loop shape having no air gap.   The coupled inductor according to any one of claims 1 to 4, wherein each of the inductor units is arranged such that each winding axis is located on the same plane parallel to the inductor installation surface.   The coupling inductor according to any one of claims 1 to 5, wherein a coupling coefficient of each inductor unit is 0.3 or more and 0.85 or less.   The coupled inductor according to any one of claims 1 to 6, wherein the core is formed of a soft magnetic powder with an insulating coating.   The coupled inductor according to claim 7, wherein the core has an initial magnetic permeability of 30 or more and 200 or less. An interleaved multi-phase switching circuit comprising the coupling inductor according to claim 1.

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